In a semiconductor device having a multilayer wiring substrate, a pattern for heat dissipation or a pattern for power supply/GND having a large area is provided in the lowermost wiring layer of the multilayer wiring substrate in order to improve the electrical characteristics and ensure the heat dissipation path. Further, in a pattern for heat dissipation of a BGA (Ball Grid Array), for example, a plurality of solder balls for heat dissipation are provided, so that the heat is conducted to the mounting board (mother board) via these solder balls.
Note that a structure of a plastic wiring substrate having two wiring layers is disclosed in, for example, Japanese Patent Application Laid-Open Publication No. H10-303334 (Patent Document 1). Also, a structure of a multilayer wiring substrate having four wiring layers is disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 2006-147676 (Patent Document 2) and Japanese Patent Application Laid-Open Publication No. 2014-123783 (Patent Document 3). Further, a land for a solder ball of the NSMD (Non-Solder Mask Defined) structure in a wiring substrate is disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 2014-103152 (Patent Document 4).